Because it’s not just water we’re pouring in there.

Fill up the first tank, and then pour a third glass of water into the pot of the tree.

This will cause the tree to spontaneously grow an orange, in accordance with the well known biological principle of instant growth.

Head back to the cabinet – within, you’ll find a juicer. Use the glass on the juicer, and then the orange on the juicer.

Make sure to do it in that order or you’ll just make a mess and have to do the whole thing over again.

Once you’ve filled up the tanks this far, you’re home free. Simply mix orange juice and water in the third and final tank, and everything will be ready!

Aren’t you glad you didn’t at any point think that painting behind the potted plant had something to do with this?

Turn off the game sound and hit the valve to release the liquid.

The bird, having drunk this carefully specified sequence of chemicals, will hop around its cage, tweeting. Frustrated by the 140 character limit, it will also vent its rage in a sequence of noises that will, by some truly miraculous coincidence, indicate by its pattern the code for the third and final safe.

Once you’ve put your head back together, open the safe up and take the key.

I leave this final, truly fiendish puzzle as an exercise for the reader.